Toronto (Nov. 15, 2006) - Fears about the possibility of vaccination related injuries have existed since the discovery of the world's first vaccine for smallpox. These fears have often not been substantiated by evidence and, at times, have undermined the many benefits of vaccination programs.

However, in some cases there is a kernel of truth in the possibility of vaccine related injury. One example of such an instance, and its consequences, occurred in 1976 in the US. Anticipating a swine flu epidemic American public health officials embarked upon a mass immunization campaign. Tragically, some of the vaccinated developed a serious autoimmune condition called Guillain-Barré syndrome(GBS) and the program had to be halted. Subsequent studies identified that people who received the swine flu vaccine were 4 to 8 times more likely to develop GBS. Compounding matters was that the swine flu epidemic never emerged.

A recently published study from Ontario, demonstrating an association between current influenza vaccines and GBS, may rekindle fears of influenza vaccine risks. However, these fears need to be taken in context, recognizing the very low risk associated with the influenza vaccine and the harms associated with the influenza virus. The best way to manage these risks, maintain the trust of the public and encourage vaccination will be to modify current policies.

Our study identified that people who received the influenza vaccine had an increased risk of being hospitalized with Guillain-Barré syndrome within 2 months of vaccination. Guillain-Barré syndrome is an extremely rare disease. Only about one in a 100 000 people could be expected to develop the condition in a year. But, it can be serious. The condition often causes paralysis starting in the lower part of the body and progressing upwards. While 90% of individuals ultimately will fully recover, a small percentage may end up on mechanical ventilation if their respiratory muscles fail.

I believe that the risk associated with the influenza vaccine in this study is real. I also believe that this risk is extremely low. The 45% increase in risk identified in our study only translates into 1 to 2 extra hospitalizations for GBS for every 1 million people vaccinated. We also found increasing vaccination rates in Ontario did not increase the rate of GBS. This strongly suggests that the vast majority of individuals develop this condition for non-influenza vaccine related reasons.

Given these facts I still plan to get the influenza vaccine for several reasons. First, as a health care worker there is high quality evidence that being vaccinated will reduce deaths amongst my patients. Second, a study in Japan found that when children were vaccinated against influenza, deaths among the elderly declined. When they stopped vaccinating children the death rates among the elderly increased. This evidence is sufficient to convince me to be vaccinated to protect the elderly family members with whom I am in contact. Third, having a young child and knowing the complications from influenza amongst children, I will accept a small risk to protect my child's health. Ultimately the decision to be vaccinated is an individual one. However, given the potential societal benefits of an individual getting vaccinated, policymakers need to ensure that programs are designed to encourage vaccination. The following suggestions may help in this respect. Everyone who receives a flu vaccine should be informed of the risk of GBS and the risk should be placed in context. This will encourage trust and prevent the magnitude of the risk from being distorted by rumours. In fields where influenza vaccination is encouraged and expected, such as health care, no-fault compensation should be provided to those rare individuals who suffer a vaccine related injury. Finally, we need to expand and further invest in programs that monitor for adverse events from vaccines. While these principles are intended for the influenza vaccination program, I believe they should be general tenets of all of our vaccination programs.

Vaccination is one of the most effective public health initiatives to reduce the burden of infectious disease. And like all health care interventions there is a potential risk associated with it. My belief is that the risk of GBS from the influenza vaccine is so low that the decision on whether or not to be vaccinated should be based on the benefit of the vaccine to your health and the health of those with whom you are in contact.

Dr. Kumanan Wilson is an Associate Professor of Medicine at University of Toronto and in specialist at the Toronto General Hospital. He is an author on the study examining the link between GBS and the influenza vaccine.

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